Radio base station device, radio network control device, and transfer rate decision method

ABSTRACT

A radio base station apparatus in a communication system in which best effort type transmission is carried out between the radio base station apparatus and mobile terminal apparatus through a wireless channel, capable of reducing a wait time in a buffer. The radio base station apparatus ( 300 ) is provided with a determining section ( 308 ) that determines a transfer rate of data transferred from a radio network control apparatus ( 500 ), a storage section ( 304 ) that temporarily stores data transferred from the radio network control apparatus at the transfer rate, a transmission section ( 301 ) that transmits the data stored in the storage section to a mobile terminal apparatus by radio, a wait time measuring section ( 306 ) that measures a wait time of data in the storage section and a transmission rate calculation section ( 307 ) that calculates an average transmission rate of data transmitted by radio to the mobile terminal apparatus, wherein the determining section ( 308 ) regards a value obtained by multiplying the average transmission rate by a coefficient according to the wait time as the transfer rate.

TECHNICAL FIELD

The present invention relates to a radio base station apparatus, etc.,in a mobile communication system in which a so-called best effort typetransmission scheme is applied to a communication between a mobileterminal apparatus and radio base station apparatus.

BACKGROUND ART

Various studies are being currently conducted on the application of anHSDPA (High Speed Downlink Packet Access) technology to datatransmission between a mobile terminal apparatus and radio base stationapparatus in a mobile communication system. The HSDPA is a technology,standardization of which the 3GPP (3rd Generation Partnership Project)is fostering (e.g., see 3GPP, TS25.401 UTRAN overall description,V3.10.0 and 3GPP, TR25.858 Physical layer aspects of UTRA High SpeedDownlink Packet Access, V5.0.0). The HSDPA realizes speed enhancement ofa downlink from a radio base station apparatus to a mobile terminalapparatus by applying to a wireless channel, adaptive modulation, H-ARQ(Hybrid Automatic Repeat reQuest), high-speed selection of a mobileterminal apparatus at the communication destination and adaptive controlof transmission parameters, etc., according to a situation of thewireless channel.

The HSDPA is a transmission scheme whereby one wireless channel isshared by a plurality of mobile terminal apparatuses, and therefore theHSDPA provides a best effort type communication. In the HSDPA, aplurality of mobile terminal apparatuses report the channel condition oftheir downlink channels to the radio base station apparatus and theradio base station apparatus schedules the order in which data istransmitted to the plurality of mobile terminal apparatuses.

In order to realize high-speed data transmission such as HADPA in awireless section between a mobile terminal apparatus and radio basestation apparatus, there is a strong demand for a flow controltechnology capable of improving data transmission throughput in a wiredsection between the radio base station apparatus and radio networkcontrol apparatus. Conventional flow control in the wired sectionbetween the radio base station apparatus and radio network controlapparatus will be explained below.

FIG. 1 is a block diagram showing the configuration of a conventionalmobile communication system.

The mobile communication system shown in FIG. 1 is constructed of amobile terminal apparatus 1, a radio base station apparatus 3, a radionetwork control apparatus 5 and a core network 6. The mobile terminalapparatus 1 and radio base station apparatus 3 are connected through awireless channel 2. On the other hand, the radio base station apparatus3 and radio network control apparatus 5 are connected through a wiredchannel 4.

The radio network control apparatus 5 transfers data input from the corenetwork 6 to the radio base station apparatus 3 through the wiredchannel 4 according to flow control. The transferred data is received bya reception section 38 and stored in a buffer 34 temporarily. Thistemporarily stored data is input to a radio transmission section 31according to scheduling determined by a scheduling section 33 accordingto the channel condition of a downlink channel, subjected topredetermined radio processing by the radio transmission section 31, andthen sent to the mobile terminal apparatus 1 through the wirelesschannel 2. Furthermore, a transfer parameter determining section 35determines a transfer parameter for flow control based on an amount ofdata stored in the buffer 34. The transfer parameter is sent from atransmission section 37 to the radio network control apparatus 5 throughthe wired channel 4.

The transmission section 37 and reception section 38 exist in an FP(Frame Protocol) processing section 36 of the radio base stationapparatus 3 and carries out transmission/reception based on an HS-DSCHFP (High Speed Downlink Shared Channel Frame Protocol). On the otherhand, the scheduling section 33, buffer 34 and transfer parameterdetermining section 35 exist a MAC-hs (Medium Access Control used forhigh speed) processing section 32 of the radio base station apparatus 3.

Next, the conventional flow control will be explained. The conventionalflow control is carried out based on the amount of data stored in thebuffer 34. That is, when the transfer parameter determining section 35sets a threshold for the amount of data stored in the buffer 34 and theamount of data stored in the buffer 34 is not less than the threshold,the transfer parameter determining section 35 determines a transferparameter for instructing the radio network control apparatus 5 to stopthe data transfer and then when the amount of data stored in the buffer34 falls below the threshold, the transfer parameter determining section35 determines a transfer parameter for instructing the radio networkcontrol apparatus 5 to restart the data transfer.

The transfer parameter consists of “credits” which indicates the amountof data to be transferred through one data transfer process, “interval”which indicates intervals at which the data transfer process is repeatedand “repetition period” which indicates the number of times the datatransfer process is repeated.

Thus, the radio base station apparatus 3 instructs the radio networkcontrol apparatus 5 on a transfer stop and transfer restart based on theamount of data stored in the buffer 34, and can thereby prevent datatransferred from the radio network control apparatus from overflowingthe buffer 34 or prevent the buffer 34 from becoming empty, which wouldinterrupt data transmission to the mobile terminal apparatus 1.

Here, since data transmission from the radio base station apparatus 3 tothe mobile terminal apparatus 1 through the wireless channel 2 iscarried out according to the best effort type HSDPA, the datatransmission rate varies with time. Furthermore, the above describedconventional flow control always tries to keep the amount of data storedin the buffer 34 of the radio base station apparatus 3 constantregardless of a variation in the transmission rate between the radiobase station apparatus 3 and the mobile terminal apparatus 1. Therefore,the time (wait time) during which data is stored in the buffer 34changes according to the transmission rate between the radio basestation apparatus 3 and mobile terminal apparatus 1. For example, whenthe amount of data stored in the buffer 34 is 64 kbits, the wait time is1 sec if the transmission rate is 64 kbps, the wait time is 2 sec if thetransmission rate is 32 kbps and the wait time is 4 sec if thetransmission rate is 16 kbps. That is, the lower the transmission ratebetween the radio base station apparatus 3 and mobile terminal apparatus1, the greater the wait time becomes.

Furthermore, when data is discarded due to a transmission error whichoccurs during transmission between the radio base station apparatus 3and mobile terminal apparatus 1, data is retransmitted from the radionetwork control apparatus 5 according to a retransmission request fromthe mobile terminal apparatus 1. When the transmission rate between theradio base station apparatus 3 and mobile terminal apparatus 1 is low,the wait time in the buffer 34 increases, and therefore theretransmitted data does not immediately arrive at the mobile terminalapparatus 1. When data does not arrive at the mobile terminal apparatus1 even if a predetermined time has passed, the radio network controlapparatus 5 repeats retransmission of the same data. When theretransmission count reaches a predetermined threshold, the radionetwork control apparatus 5 sends a reset message to the mobile terminalapparatus 1. The mobile terminal apparatus 1 which has received thisreset message sends j an ACK (ACKnowledgement: positive response) inresponse to the reset message to the radio network control apparatus 5and discards all data stored in the own apparatus. Furthermore, theradio network control apparatus 5 which has received the ACK alsodiscards all data stored in the own apparatus. Thus, when all datastored in the mobile terminal apparatus 1 and radio network controlapparatus 5 are discarded, their communication is interrupted.

Furthermore, due to a delay in the buffer 34 of the radio base stationapparatus 3, if a reset message sent by the radio network controlapparatus 5 does not immediately arrive at the mobile terminal apparatus1 and as a result, the radio network control apparatus 5 may repeatretransmission of the reset message. In this case, when theretransmission count of the reset message reaches a predeterminedthreshold, the radio network control apparatus 5 decides that there issome error in the wireless channel 2 and disconnects the wirelesschannel 2 used by the mobile terminal apparatus 1. When the wirelesschannel 2 is disconnected in this way, the mobile terminal apparatus 1can no longer receive the communication service which has been used sofar.

The above described problem will be explained more specifically using asequence diagram. FIG. 2 is an operation sequence diagram of aconventional mobile communication system.

First, the transfer parameter determining section 35 of the radio basestation apparatus 3 confirms that the amount of data stored in thebuffer 34 is not greater than the threshold and determines a transferparameter for permitting the data transfer. This transfer parameter issent from the transmission section 37 to the radio network controlapparatus 5.

The radio network control apparatus 5 starts the data transfer accordingto the instruction of the received transfer parameter. The data 0 to 127transferred from the radio network control apparatus 5 are stored in thebuffer 34 of the radio base station apparatus 3. Then, according toscheduling at the scheduling section 33, the data stored in the buffer34 are sequentially sent from the radio transmission section 31 to themobile terminal apparatus 1.

At this time, suppose that data 0 is discarded due to a transmissionerror in the wireless channel 2. When the mobile terminal apparatus 1receives next data 1, it detects from the discontinuity of the sequencenumber that data 0 has been discarded during transmission. As a reportof the reception condition, the mobile terminal apparatus 1 transmits aretransmission request of data 0 (retransmission request 0) to the radionetwork control apparatus 5. At the same time, the mobile terminalapparatus 1 starts a timer for controlling intervals of reporting of thereception condition. When the radio network control apparatus 5 receivesthe retransmission request 0, it retransmits data 0.

The retransmitted data 0 is stored in the buffer 34 of the radio basestation apparatus 3. However, since all the previously stored data havenot been transmitted yet, retransmitted data 0 is not immediatelytransmitted to the mobile terminal apparatus 1. Until the retransmitteddata 0 is sent to the mobile terminal apparatus 1, the radio basestation apparatus 3 sends other data stored in the buffer 34 (data 2 to127) to the mobile terminal apparatus 1 sequentially. That is, theretransmitted data 0 remains stored in the buffer 34 until data 127 issent. As a result, as shown in FIG. 2, the wait time of data 0 in thebuffer 34 becomes enormous.

Moreover, the mobile terminal apparatus 1 has not received data 0 whoseretransmission is requested yet even when the timer times out, andtherefore the mobile terminal apparatus 1 sends a retransmission request0 to the radio network control apparatus 5 again. Every time the radionetwork control apparatus 5 retransmits the same data (data 0), itcounts up a transmission count (D) and when this value reaches apredetermined number of times (4 in the example of FIG. 2), the radionetwork control apparatus 5 sends a reset message to the mobile terminalapparatus 1. As described above, this causes all the data stored in theradio network control apparatus 5 and mobile terminal apparatus 1 to bediscarded.

Furthermore, when the reset message sent from the radio network controlapparatus 5 does not immediately arrive at the mobile terminal apparatus1 due to a delay in the buffer 34, the radio network control apparatus 5retransmits a reset message every time the timer times out. Every timethe radio network control apparatus 5 transmits a reset message, itcounts up a transmission count (R) and when this value reaches apredetermined number of times (3 in the example of FIG. 2), the radionetwork control apparatus 5 decides it as an error of the wirelesschannel 2 and disconnects the wireless channel 2 used by the mobileterminal apparatus 1.

Thus, the conventional flow control based on only a wait time in thebuffer can be hardly attuned to a communication system (e.g., the abovedescribed HSDPA) in which best effort type transmission is carried outthrough a wireless channel between the radio base station apparatus andmobile terminal apparatus.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a radio base stationapparatus, etc., in a communication system in which best effort typetransmission is carried out through a wireless channel between the radiobase station apparatus and a mobile terminal apparatus, capable ofreducing a wait time in a buffer.

According to an aspect of the present invention, the radio base stationapparatus comprises a determining section that determines a transferrate of data transferred from a radio network control apparatus, astorage section that temporarily stores data transferred from the radionetwork control apparatus at the transfer rate, a transmission sectionthat transmits the data stored in the storage section to a mobileterminal apparatus by radio, a wait time measuring section that measuresa wait time of the data in the storage section and a transmission ratecalculation section that calculates an average transmission rate of datatransmitted to the mobile terminal apparatus by radio, wherein thedetermining section uses a value obtained by multiplying the averagetransmission rate by a coefficient according to the wait time as thetransfer rate.

The radio base station apparatus preferably further comprises a dataamount measuring section that measures the amount of data stored in thestorage section, wherein the wait time measuring section regards a valueobtained by dividing the amount of data measured by the data amountmeasuring section by the average transmission rate calculated by thetransmission rate calculation section as the wait time.

The radio base station apparatus preferably further comprises a dataamount measuring section that measures an amount of data stored in thestorage section, wherein the transmission rate calculation sectioncalculates an actual average transmission rate when the amount of datameasured by the data amount measuring section is equal to or greaterthan a threshold and calculates a virtual average transmission rate whenthe amount of data measured by the data amount measuring section is lessthan the threshold.

The radio base station apparatus preferably further comprises an addingsection that adds time information to data when the data is input to thestorage section, wherein the wait time measuring section measures thewait time from the time indicated by the time information and the timeat which the data is output from the storage section.

According to another aspect of the present invention, a radio networkcontrol apparatus comprises a transfer section that transfers data tothe radio base station apparatus at a transfer rate determined by theradio base station apparatus and a control section that performsretransmission control of data based on a selective retransmission typeretransmission control protocol, wherein the transfer section notifiesthe control section of the transfer rate so as to match the transferrate at the transfer section to the transfer rate at the controlsection.

According to a further aspect of the present invention, the transferrate determining method is a transfer rate determining method used at aradio base station apparatus, comprising the steps of determining atransfer rate of data transferred from a radio network controlapparatus, temporarily storing data transferred from the radio networkcontrol apparatus at the transfer rate in a buffer and sending the datastored in the buffer to a mobile terminal apparatus by radio, wherein avalue obtained by multiplying an average transmission rate of data sentto the mobile terminal apparatus by radio by a coefficient according toa wait time of data in the buffer is regarded as a transfer rate of thedata transferred from the radio network control apparatus.

The transfer rate determining method preferably sets the transfer rateof data transferred from the radio network control apparatus to 0 tostop the data transfer when the amount of data stored in the buffer isequal to or greater than a threshold.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the configuration of a conventionalmobile communication system;

FIG. 2 is an operation sequence diagram of the conventional mobilecommunication system;

FIG. 3 is a block diagram showing the configuration of a mobilecommunication system according to an embodiment of the presentinvention;

FIG. 4 is a table stored in the radio base station apparatus accordingto the embodiment of the present invention;

FIG. 5 is a block diagram showing the configuration of another radiobase station apparatus according to the embodiment of the presentinvention;

FIG. 6 is a block diagram showing the configuration of the radio networkcontrol apparatus according to the embodiment of the present invention;and

FIG. 7 is an operation sequence diagram of the mobile communicationsystem according to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference now to the attached drawings, an embodiment of thepresent invention will be explained in detail below. FIG. 3 is a blockdiagram showing the configuration of a mobile communication systemaccording to an embodiment of the present invention.

The mobile communication system shown in FIG. 3 is constructed of amobile terminal apparatus 100, a radio base station apparatus 300, aradio network control apparatus 500 and a core network 600. The mobileterminal apparatus 100 and the radio base station apparatus 300 areconnected by a wireless channel 200. Furthermore, the radio base stationapparatus 300 and radio network control apparatus 500 are connected by awired channel 400. Furthermore, since the wireless channel 200 carriesout best effort type transmission, the transmission rate varies withtime.

The radio network control apparatus 500 transfers data input from thecore network 600 to the radio base station apparatus 300 through thewired channel 400 at a transfer rate instructed from the radio basestation apparatus 300. The transferred data is received by a receptionsection 311 of the radio base station apparatus 300 and temporarilystored in a buffer 304. This temporarily stored data is input to a radiotransmission section 301 according to scheduling determined by ascheduling section 303 according to a channel condition of a downlinkchannel, subjected to predetermined radio processing at the radiotransmission section 301 and then transmitted to the mobile terminalapparatus 100 through the wireless channel 200.

A data amount measuring section 305 measures an amount of data stored inthe buffer 304. The amount of data measured is notified to a wait timemeasuring section 306 and a transmission rate calculation section 307.

The transmission rate calculation section 307 calculates an averagetransmission rate of data transmitted to the mobile terminal apparatus100 by radio based on information from the scheduling section 303. Thescheduling section 303 sends the transmission rate calculation section307 a scheduling result, that is, information indicating what amount ofdata of which time slot (which time) has been actually sent to whichmobile terminal apparatus or what amount of data could have beentransmitted if the communication environment had been such that wouldalways give a transmission opportunity. Thus, the transmission ratecalculation section 307 can determine an actual average transmissionrate or virtual average transmission rate for each mobile terminalapparatus. For example, when data having a total of 320 kbits for 10 sechas been actually transmitted to the mobile terminal apparatus 100, theactual average transmission rate is calculated to be 32 kbps.Furthermore, in the case where though only an opportunity oftransmitting data having a total of 320 kbits for 10 sec has beenactually given, data having a total of 3 Mbits could have beentransmitted if an opportunity for always transmitting data for 10 sechad been given, the virtual average transmission rate is calculated tobe 300 kbps. The transmission rate calculation section 307 calculateseither the actual average transmission rate or virtual averagetransmission rate according to the amount of data measured by the dataamount measuring section 305. That is, when the amount of data measuredby the data amount measuring section 305 is equal to or greater than athreshold, the actual average transmission rate is calculated and whenthe amount of data measured by the data amount measuring section 305 isless than the threshold, the virtual average transmission rate iscalculated. Thus, the method of calculating an average transmission rateis changed based on the amount of data stored in the buffer 304 and theradio base station apparatus 300 can thereby instruct the radio networkcontrol apparatus 500 on an optimal transfer rate even when burst-liketraffic occurs. Moreover, the average transmission rate calculated inthis way is notified to the wait time measuring section 306 and transferrate determining section 308.

When there is substantially no possibility that burst-like traffic mayoccur, instead of changing the method of calculating the averagetransmission rate as described above, it is also possible to use eitherthe actual average transmission rate or virtual average transmissionrate in a fixed manner.

The wait time measuring section 306 measures the data wait time in thebuffer 304. The wait time measuring section 306 measures the data waittime in the buffer 304 from the amount of data measured by the dataamount measuring section 305 and the transmission rate calculated by thetransmission rate calculation section 307 according to followingExpression (1):Wait time=data amount in buffer 304/average transmission rate  (1)

That is, the wait time measuring section 306 regards a value obtained bydividing the amount of data measured by the data amount measuringsection 305 by the average transmission rate calculated by thetransmission rate calculation section 307 as a data wait time in thebuffer 304. Calculating the wait time in this way also makes it possibleto predict a future wait time and consequently perform appropriate flowcontrol. The wait time measured in this way is notified to the transferrate determining section 308.

The transfer rate determining section 308 determines a transfer rate ofdata transferred from the radio network control apparatus 500 to theradio base station apparatus 300 from the average transmission ratecalculated by the transmission rate calculation section 307 and the waittime measured by the wait time measuring section 306 according tofollowing Expression (2):Transfer rate=average transmission rate×α  (2)

Here, coefficient α in Expression (2) above is a coefficient determinedaccording to the wait time, varies between 0 and 1 and decreases as thewait time increases. For example, the transfer rate determining section308 has a table shown in FIG. 4 and calculates a coefficient α accordingto the wait time. In the example of FIG. 4, α=1 when the wait time is 0to 100 ms, α=0.7 when the wait time is 100 ms to 200 ms, α=0.5 when thewait time is 200 ms to 300 ms, α=0.3 when the wait time is 300 ms to 400ms and α=0 when the wait time is 500 ms or above. Thus, from Expression(2) above, the transfer rate decreases as the wait time increases andthe transfer rate becomes 0 when the wait time is 500 ms or above. Thatis, when the wait time is 500 ms or above, a data transfer from theradio network control apparatus 500 to the radio base station apparatus300 is stopped. In this way, the transfer rate determining section 308determines a value obtained by multiplying the average transmission rateby a coefficient α which corresponds to the wait time as a transferrate. The transfer rate determined is notified to the transfer parameterdetermining section 309.

The transfer parameter determining section 309 determines credits(amount of data to be transferred in a first data transfer process),interval (intervals at which a data transfer process is performed) andrepetition period (count of repeating a data transfer process) oftransfer parameters so as to reach the transfer rate notified from thetransfer rate determining section 308. The transfer parametersdetermined in this way are sent from a transmission section 312 to theradio network control apparatus 500 through the wired channel 400.

Here, the wait time can also be measured from the configuration shown inFIG. 5. That is, the radio base station apparatus 300 has a TS (timestamp) adding section 313 and when data is input to the buffer 304, atime stamp which is time information is added to the data by the TSadding section 313. When the data with a time stamp is output from thebuffer 304, the wait time measuring section 306 measures a differencebetween the time indicated by the time stamp and the time at which thedata is output from the buffer 304 as a wait time. By measuring the waittime in this way, it is possible to measure the exact wait time withrespect to the current time point and consequently realize accurate flowcontrol.

The transmission section 312 and reception section 311 exist in an FP(Frame Protocol) processing section 310 of the radio base stationapparatus 300 and carry out transmission/reception based on an HS-DSCHFP (High Speed Downlink Shared Channel Frame Protocol). Furthermore, thescheduling section 303, buffer 304, data amount measuring section 305,wait time measuring section 306, transmission rate calculation section307, transfer rate determining section 308, transfer parameterdetermining section 309 and TS adding section 313 exist in a MAC-hs(Medium Access Control used for high speed) processing section 302 ofthe radio base station apparatus 300.

Next, the configuration of the radio network control apparatus 500 willbe explained. FIG. 6 is a block diagram of the radio network controlapparatus according to an embodiment of the present invention. An FP(Frame Protocol) processing section 501 receives a transfer parametersent from the radio base station apparatus 300 based on an HS-DSCH FP(High Speed Downlink Shared Channel Frame Protocol). Then, the FPprocessing section 501 transfers the data to the radio base stationapparatus 300 according to the transfer parameter. That is, the FPprocessing section 501 transfers data at a transfer rate determined bythe radio base station apparatus 300. Furthermore, the FP processingsection 501 sends the received transfer parameter to an RLC (Radio LinkControl) processing section 503 so as to match the transfer rate for thedata to be transferred to the radio base station apparatus 300 to therate of the data output from the RLC processing section 503. That is,the FP processing section 501 also notifies the RLC processing section503 of the transfer rate determined by the radio base station apparatus300.

Here, the FP processing section 501 may notify the transfer rate to theRLC processing section 503 directly or through an MAC-d processingsection 502. The RLC processing section 503 has the function of carryingout retransmission control on data based on a selective retransmissiontype retransmission control protocol and controls the rate of the dataoutput to the MAC-d processing section 502 to the transfer rate notifiedfrom the FP processing section 501.

The MAC-d (Medium Access Control used for dedicated) processing section502 carries out MAC-d processing on data input from the RLC processingsection 503 and inputs the data to the FP processing section 501.Matching the transfer rate of the data transferred to the radio basestation apparatus 300 to the rate of the data output from the RLCprocessing section 503 prevents the wait time of data in the buffer ofthe FP processing section 501 from further occurring. This furthersuppresses a transmission delay from the radio network control apparatus500 to the mobile terminal apparatus 100.

An RLC process of the selective retransmission type retransmissioncontrol protocol carried out by the RLC processing section 503 selectsand retransmits NACK and notified data from among the transmitted databased on an ACK or NACK (Negative ACKnowledgement: negative response)notified from the mobile terminal apparatus 100. Furthermore, a MAC-dprocess carried out by the MAC-d processing section 502 adds a MAC-dheader to the data input from the RLC processing section 503 and sendsthe data to the FP processing section 501. Details of the RLC processand MAC-d process are described in the 3GPP, TS25.321 Medium AccessControl (MAC) protocol specification, V3.14.0.

Next, an operation sequence will be explained using FIG. 7.

First, the radio base station apparatus 300 determines transferparameter 1 which permits a data transfer and sends it to the radionetwork control apparatus 500.

The radio network control apparatus 500 which has received this transferparameter 1 starts a data transfer according to the instruction of thereceived transfer parameter 1. Data 0 to 10 transferred from the radionetwork control apparatus 500 are stored in the buffer 304 of the radiobase station apparatus 300. Then, according to the scheduling at thescheduling section 303, the data stored in the buffer 304 aresequentially transmitted to the mobile terminal apparatus 100.

At this time, suppose that data 0 is discarded due to a transmissionerror in the wireless channel 200. When the mobile terminal apparatus100 receives next data 1, it detects from the discontinuity of thesequence number that data 0 has been discarded. As the notification ofthe reception condition, the mobile terminal apparatus 100 sends arequest for retransmission of data 0 (retransmission request 0) to theradio network control apparatus 500. At the same time, the mobileterminal apparatus 100 starts a timer for controlling intervals at whichthe reception condition is notified. When the radio network controlapparatus 500 receives retransmission request 0, it retransmits data 0at a transfer rate instructed by transfer parameter 2. Every time apredetermined time elapses after the transmission of transfer parameter1, transfer parameter 2 and transfer parameter 3 for instructing thetransfer rate determined as described above are sent from the radio basestation apparatus 300 to the radio network control apparatus 500.

The retransmitted data 0 is stored in the buffer 304 of the radio basestation apparatus 300. Here, the radio base station apparatus 300determines the transfer rate as shown above, suppresses the wait time inthe buffer 304 to a level smaller than the intervals of notification ofthe reception condition from the mobile terminal apparatus 100 (timefrom the start to end of the timer of the mobile terminal apparatus100), and therefore the retransmitted data 0 is output from the buffer304 within a time smaller than the intervals of notification of thereception condition and sent to the mobile terminal apparatus 100. As aresult, it is possible to suppress the wait time of data 0 in the buffer304 to a small level as shown in FIG. 7.

When the timer times out, the mobile terminal apparatus 100 which hasreceived data 0 notifies the radio network control apparatus 500 thatall data up to data 11 including the retransmitted data 0 have beenreceived correctly.

Then, the radio network control apparatus 500 which has received thenotification of normal reception transfers data 12 and subsequent dataat the transfer rate instructed by transfer parameter 3.

Thus, this embodiment takes into consideration both the averagetransmission rate from the radio base station apparatus to the mobileterminal apparatus and the wait time in the buffer of the radio basestation apparatus, determines the transfer rate from the radio networkcontrol apparatus to the radio base station apparatus, matches thetransfer rate to the rate of the data output from the RLC processingsection of the radio network control apparatus, and can thereby preventthe radio network control apparatus from transferring an excessiveamount of data to a lower layer.

Furthermore, this embodiment reduces the time required for retransmitteddata to arrive at the mobile terminal apparatus even when dataretransmission occurs, and can consequently prevent all data stored inthe radio network control apparatus and mobile terminal apparatus frombeing discarded and prevent the wireless channel used by the mobileterminal apparatus from being disconnected.

When a threshold is set for a data amount in the buffer 304 of the radiobase station apparatus 300 and the amount of data stored in the buffer304 exceeds the threshold, it is also possible to set the transfer rateto 0 and thereby stop a data transfer to the radio network controlapparatus 500 and on the contrary when the amount of data stored in thebuffer 304 is smaller than the threshold, it is possible to carry outflow control using the above described transfer rate determining method.By so doing, it is possible to reliably prevent data transferred fromthe radio network control apparatus 500 from overflowing the buffer 304.

As described above, the present invention can reduce a wait time in abuffer in a communication system in which best effort type transmissionis carried out between a radio base station apparatus and mobileterminal apparatus through a wireless channel.

This application is based on the Japanese Patent Application No.2003-96746 filed on Mar. 31, 2003, entire content of which is expresslyincorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention is suitable for use in a radio base stationapparatus, etc., in a mobile communication system.

1. A radio base station apparatus comprising: a determining section thatdetermines a transfer rate of data transferred from a radio networkcontrol apparatus; a storage section that temporarily stores datatransferred from said radio network control apparatus at said transferrate; a transmission section that transmits the data stored in saidstorage section to a mobile terminal apparatus by radio; a wait timemeasuring section that measures a wait time of the data in said storagesection; and a transmission rate calculation section that calculates anaverage transmission rate of data transmitted to said mobile terminalapparatus by radio, wherein said determining section uses a valueobtained by multiplying said average transmission rate by a coefficientaccording to said wait time as said transfer rate.
 2. The radio basestation apparatus according to claim 1, further comprising a data amountmeasuring section that measures the amount of data stored in saidstorage section, wherein said wait time measuring section regards avalue obtained by dividing the amount of data measured by said dataamount measuring section by the average transmission rate calculated bysaid transmission rate calculation section as said wait time.
 3. Theradio base station apparatus according to claim 1, further comprising adata amount measuring section that measures an amount of data stored insaid storage section, wherein said transmission rate calculation sectioncalculates an actual average transmission rate when the amount of datameasured by said data amount measuring section is equal to or greaterthan a threshold and calculates a virtual average transmission rate whenthe amount of data measured by said data amount measuring section isless than the threshold.
 4. The radio base station apparatus accordingto claim 1, further comprising an adding section that adds timeinformation to data when the data is input to said storage section,wherein said wait time measuring section measures said wait time fromthe time indicated by said time information and the time at which saiddata is output from said storage section.
 5. A radio network controlapparatus comprising: a transfer section that transfers data to saidradio base station apparatus according to claim 1 at a transfer ratedetermined by said radio base station apparatus; and a control sectionthat performs retransmission control of data based on a selectiveretransmission type retransmission control protocol, wherein saidtransfer section notifies said control section of said transfer rate soas to match the transfer rate at said transfer section to the transferrate at said control section.
 6. A transfer rate determining method usedat a radio base station apparatus, comprising the steps of: determininga transfer rate of data transferred from a radio network controlapparatus; temporarily storing data transferred from said radio networkcontrol apparatus at said transfer rate in a buffer; and sending thedata stored in said buffer to a mobile terminal apparatus by radio,wherein a value obtained by multiplying an average transmission rate ofdata sent to said mobile terminal apparatus by radio by a coefficientaccording to a wait time of data in said buffer is regarded as atransfer rate of the data transferred from the radio network controlapparatus.
 7. The transfer rate determining method according to claim 6,wherein the transfer rate of data transferred from said radio networkcontrol apparatus is set to 0 to stop the data transfer when the amountof data stored in said buffer is equal to or greater than a threshold.